This invention concerns telephone network interface enclosures. Such enclosures are shown in U.S. Pat. Nos. 4,749,359, 4,800,588, 4,910,770, 4,945,559, 4,949,376 and 5,153,910, the disclosures of which are incorporated herein by reference. The enclosures include terminals to which a telephone subscriber's wiring can be connected.
Enclosures of network interface devices are generally made of either metal or plastic. Of the plastic variety there are found enclosures with removable covers and those with hinged covers. It is an object of this invention to resolve one of the problems inherent with hinges of the plastic enclosures.
Commonly, a plastic hinged cover network interface enclosure utilizes modern molding techniques to form the hinge as two complementary geometries. The two are held together by way of a plastic molded snap fit design which allows relative rotation. Furthermore, the plastic molding process allows the halves of the hinge to be integrally molded as a feature of other components and thereby minimizes the total number of parts required to manufacture a complete enclosure.
Typically, one half of the hinge geometry is found to be a pin, cylindrical in shape, integrally molded as a part of the base of the enclosure. The cover of the enclosure contains geometry complementary in shape to the pin and is semi-tubular in shape. The complementary portion of this geometry is its interior surface which can be found to encompass anywhere from 190 to 300 degrees of the pin's circumference. This is unlike other common hinges in which the pin of the hinge is entirely concealed, such as a metallic piano hinge.
The problem with molded hinges as above described is that the pin is left partially exposed and is susceptible to accumulation of foreign material. This foreign material can impede the smooth, proper function of the hinge over time. Of greater concern is the build-up of paint or stain on this exposed portion of the pin. This build-up can act as a barrier as well as a bonding agent. Both can prove to be a restriction to the rotation of the hinge which at times results in the destruction of the joint.
The benefits to manufacturers who use this plastic molded, snap fit hinge design are great. It allows economy of parts and simplicity of assembly while fully utilizing standard injection molding techniques. That is to say that no special motion in the tool is required to create the hinge members. This design provides the manufacturer a cost effective means to obtain a desirable feature. Additionally, the buyers of these products view a hinged cover as an important if not a required feature as it minimizes the possibility of losing or misplacing the cover.
Manufacturers who use this type of hinge and recognize its benefits as well as its short comings have tried a variety of ideas in hopes of reducing the potential for destructive damage to their product. One common approach has been to construct the hinge members substantially larger than the hinging function would require in the absence of obstruction or bonding agents. The perception is that a larger hinge is a stronger hinge. Others have tried arranging the hinge geometry so that an obstruction causes the snap fit joint between the cover and the base to decouple non-destructively. While this method may prevent damage, it is viewed as an inconvenience. Still others arrange the geometry in efforts to minimize the exposed area of the pin. The nature of plastic materials and molding processes limit the degree to which this last method is effective.